The Advanced Television Systems Committee (ATSC) standard for Digital Television (DTV) in the United States requires an 8-Vestigial Sideband (VSB) transmission system which includes Forward Error Correction (FEC) as a means of improving the system performance. The FEC system consists of a Reed-Solomon encoder, followed by a byte interleaver, and a trellis encoder on the transmitter side. At the receiver end, there is a corresponding trellis decoder, byte deinterleaver and Reed-Solomon decoder. The ATSC-DTV standard is document A53.doc, dated Sep. 16, 1995 produced by the United States Advanced Television Systems Committee. FIG. 1 shows a simplified block diagram of the DTV transmitter and receiver, emphasizing the FEC system.
The ATSC has started a study group to create a new M/H (mobile/handheld) DTV standard that is backwards compatible with the current DTV standard (A/53), more robust, more flexible, and provides expanded services to customers utilizing mobile and handheld devices. The new proposals have added a new layer of FEC coding and more powerful decoding algorithms to decrease the Threshold of Visibility (TOV).
The added layer of FEC coding requires decoding techniques such as turbo decoding discussed in an article by C. Berrou, A. Glavieux and P. Thitimajshima, entitled “Near Shannon Limit Error—Correcting Coding and Decoding: Turbo-Codes,” found in Proceedings of the IEEE International Conference on Communications—ICC'93, May 23-26, 1993, Geneva, Switzerland, pp. 1064-1070. A discussion of turbo coding can be found in the article by M. R. Soleymani, Y. Gao and U. Vilaipornsawai, entitled “Turbo Coding for Satellite and Wireless Communications,” Kluwer Academic Publishers, USA, 2002.
Decoding of signals encoded for ATSC DTV with an added FEC layer can also involve trellis decoding algorithms like maximum a posteriori (MAP) decoders as described by L. R. Bahl, K. Cocke, F. Jelinek and J. Rariv, in an article entitled “Optimal Decoding of Linear Codes for Minimizing Symbol Error Rate,” found in IEEE Transactions on Information Theory, Vol. IT-20, No. 2, March 1974, pp. 284-287. Another discussion of trellis coders and a MAP decoder is found in an article written by A. J. Viterbi, entitled “An Intuitive Justification and a Simplified Implementation of the Map Decoder for Convolutional Codes,” found in IEEE Journal on Selected Areas in Communications, Vol. 16, No. 2, February 1998, pp. 260-264.
In addition, the FEC system may allow for transmission with time diversity as described by International Patent Applications WO 2008/144004 and 2009/064468. Although the proposed systems attempt to provide backwards compatibility with the current DTV standard, no other known system permit diversity within their coding structure.
This arrangement proposes a processor that recovers decodable data blocks in a mobile DTV stream with diversity, implemented using a small memory size and minimal latency.